Although we’ve examined the effects of soy on male humans and male monkeys, we’ve yet to write in detail about its effects on women. Here we examine some of the common negative side effects attributed to soy consumption in women.

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Over the past few months, we’ve looked in detail at the feminising effects of a variety of naturally and artificially produced substances – phytoestrogens and xenoestrogens, respectively – on the hormonal balance and health of men. And monkeys – really. In fact, our article on the serious negative effects of long-term soy consumption on male macaques remains our most popular article to date, featuring in various mainstream media outlets and even being posted by Joe Rogan on his Instagram page.

Click here to read out one-stop primer on endocrine (hormone)-disruptors. Everything you need to know in 2021 about xenoestrogens and phytoestrogens is contained here.

The effects of soy phytoestrogens are not limited to male humans and monkeys. Women, too, can experience substance hormonal and other physiological changes as a result of soy consumption, and in this article we’ll consider some of the most common effects it can have.

Click here to read about how Japanese researchers were able to totally feminise male catfish using soy compounds.

What Women Should Know About Soy

Menstrual disruption and Fertility

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In our article on beer, we reported that female hop-pickers commonly experienced menstrual disturbances simply through handling hops, because of the powerful phytoestrogens they contain. Well, the same appears to be true with soy, as many anecdotal reports and a number of studies suggest.

We know that soy consumption can cause reduced fertility in men, and there is some evidence that the same is true of women (see also this study).

As with the evidence for cancer, discussed below, there is some argument about whether or not the evidence for fertility effects is real. This 2020 study, for instance, claims that there are no effects.

Early Puberty

Age of Puberty Trends

The changing age of puberty in girls, according to a German study

The age of puberty has been dropping dramatically over the last few decades, and it’s now increasingly common for a girl to reach menarche between ages 8 through 10. 

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Soy has been strongly tied to early puberty in females. Not only is the amount of soy a young girl eats a contributing factor, the soy the mother consumes during pregnancy can also influence puberty age

Changes to reproductive tissues have been observed in babies fed soy formula.

Recently, we reported on a study of infants given soy formula, which showed that they had 22,000 times more estrogen in their bodies than babies breastfed babies – the equivalent of consuming FIVE whole birth-control pills. Shocking!

Persistent sexual arousal

While estrogen – and thus soy – is often recommended to enhance diminished female libido, in at least one documented case, the enhancement caused by soy consumption was so great that the woman was unable to control herself. Quite literally. Removing soy from her diet reduced her symptoms significantly.

So unless you like the idea of starring in your own version of a Lars Von Trier film, it may be a good idea not to go overboard with your soy consumption.



The C-word. A word nobody wants to hear.

For many years, women with cancer, especially breast cancer, have been advised not to eat soy products, because of a perceived risk that the phytoestrogens might aggravate the cancer.

Things aren’t quite so clear, however.

“There has long been a paradox concerning genistein, which has the similar structure as estrogen and activates both human estrogen receptors to a degree. Estrogen drives most breast cancer growth, yet high soy intake among women in Asian countries has been linked to a breast cancer rate that is five times lower than Western women, who eat much less soy,” says one expert. “So why is soy, which mimics estrogen, protective in Asian women?”

What it may come down to, according to one study, is whether soy consumption begins before or after cancer develops. If soy has been consumed before cancer develops, it may be safe to continue consuming it; but if soy consumption begins only after cancer has developed, the phytoestrogens may aggravate the cancer.

A number of other studies have suggested that soy consumption may have protective effects for women not just in breast cancer (see this study, for instance), but in other forms of cancer too, such as lung cancer.

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